Medical systems for tissue therapy often require the implantation of one or more medical elements proximate to a target tissue site. The medical element may be, for example, a medical lead to deliver electrical stimulation energy to the tissue or a catheter to deliver a fluid to the tissue. In order to implant the medical element in a patient, a clinician may generate a medical image of the target tissue site for the medical element and guide the medical element into the patient based on the generated image.
For some tissue stimulation applications, an electrical stimulation lead is implanted near a sacral nerve, which is a nerve bundle within the sacrum, a large triangular bone situated at the lower part of the vertebral column and at the upper and back part of the human pelvic cavity. There are multiple sacral nerves that pass through anterior and posterior sacral foramina of the sacrum. The lead may include one or more stimulation electrodes, one or more sensing electrodes, or combinations thereof.
Electrical stimulation of one or more sacral nerves may eliminate or reduce some pelvic floor disorders by influencing the behavior of the relevant structures, such as the bladder, sphincter and pelvic floor muscles. Pelvic floor disorders include urinary incontinence, urinary urge/frequency, urinary retention, pelvic pain, bowel dysfunction, and male and female sexual dysfunction. The organs involved in bladder, bowel, and sexual function receive much of their control via the second, third, and fourth sacral nerves, commonly referred to as S2, S3 and S4 respectively. Electrical stimulation is typically delivered to at least one of the S2, S3, or S4 sacral nerves using an electrical stimulator, which is coupled to a stimulation lead that is implanted on a temporary or permanent basis proximate to the relevant sacral nerve.
In some cases, a medical element of a medical system is implanted through a sacral foramen (a single foramina) of a patient. For example, if selective stimulation of the S3 sacral nerve is desired, a medical lead may be introduced into the sacral foramen corresponding to the S3 sacral segment, which is commonly referred to as the “S3 sacral foramen.” In one technique, a hollow introducer needle is advanced through the S3 foramen and the lead is advanced through a lumen of the hollow introducer needle until one or more electrodes near a distal end of the lead are positioned near the S3 sacral nerve. Stimulation energy is applied through the lead to the electrode to test the S3 nerve response. If necessary, the one or more electrodes are moved back and forth to locate the most efficacious location.
Once in position, the lead may be secured by suturing the lead body to subcutaneous tissue posterior to the sacrum or using an anchoring mechanism such as tines carried by the lead, sutures or another technique. The lead may then be attached directly or indirectly (e.g., via an extension) to the output of an implantable electrical stimulator, although in some cases, the lead may be attached to an external pulse generator for temporary trial stimulation.